Sample Question Paper
Class XII (2015-16)
Biology (044)
Time allowed: 3 Hrs
Maximum Marks: 70
General Instructions:
1. There are a total of 26 questions and five sections in the question paper. All questions
are compulsory.
2. Section A contains question number 1 to 5, Very Short Answer type questions of one
mark each.
3. Section B contains question number 6 to 10, Short Answer type I questions of two
marks each.
4. Section C contains question number 11 to 22, Short Answer type II questions of three
marks each.
5. Section D contains question number 23, Value Based Question of four marks.
6. Section E contains question number 24 to 26, Long Answer type questions of five
marks each.
7. There is no overall choice in the question paper; however, an internal choice is
provided in one question of two marks, one question of three marks and all three
questions of five marks. An examinee is to attempt any of the questions out of the two
given in the question paper with the same question number.
SECTION -A
1.
Observe the pedigree chart and answer the following questions:
(a)
Identify whether the trait is sex-linked or autosomal.
(b)
Give an example of a disease in human beings which shows such a pattern of
inheritance.
[½ + ½=1]
2.
Identify the reason for selection of DNA polymerase from Thermus aquaticus for
Polymerase Chain Reaction.
[1]
3.
Govt. of India has raised the marriageable age of female to 18 yrs and of males to 21 yrs.
Suggest any two more measures adopted by Government for the purpose.
[½ + ½=1]
4.
Thymus of a new born child was degenerating right from birth due to a genetic disorder.
Predict its two impacts on the health of the child.
[½ + ½=1]
5.
Give an example of a chromosomal disorder caused due to non-disjunction of autosomes.
[1]
SECTION -B
6.
During an excavation assignment, scientists collected pollen grains of a plant preserved in
deeper layers of soil. Analyse the properties of pollen grains which help in the fossilization.
[½+½ x3= 2]
7.
Protein synthesis machinery revolves around RNA but in the course of evolution it was
replaced by DNA. Justify.
[2]
8.
Identify two ways in which Spirulina is helpful to mankind.
OR
[1+1=2]
Keeping beehives in crop fields has several advantages. List any two.
[1+1=2]
9.
Suryakant had banana plantation in his field. Quality of the fruit was excellent but the yield
suffered due to infection of the plants by a virus. Suggest a fast and efficient method to get
healthy and a large number of plants in the next generation without compromising on the
existing quality. Justify the selection of your method.
[2]
10.
Besides acting as ‘conduits’ for energy transfer across trophic levels, predators play other
important roles. Justify.
[2]
SECTION -C
11.
Explain three outbreeding devices.
12.
After implantation interdigitation of maternal and foetal tissues takes place. Identify the
tissues involved and justify their role.
[1+1+1=3]
13.
Compare the two ecological pyramids of biomass given below and explain the situations in
which this is possible. Also construct an ideal pyramid of energy if 200,000 joules of
sunlight is available.
[1+2=3]
14.
With respect to Messelson and Stahl’s Experiment, answer the following questions:
15.
[1+1+1=3]
(a)
Identify the method used to distinguish between heavy and light isotopes of
nitrogen.
(b)
With the help of diagrams, compare the results for the DNA isolated after 20
minutes of experiment with the DNA which was isolated after 40 minutes.
[1+2=3]
A student was simulating Urey and Millers experiment to prove the origin of life. The set up
used by the student is given –
16.
(a)
Find out the reasons why he could not get desired results.
(b)
What conclusion was drawn by Urey and Miller through this experiment?
(c)
Compare the conclusion drawn with the theory of spontaneous generation.
[1+1+1=3]
Given below is a figure of a biogas plant.
(a)
Identify A and justify its floating nature.
(b)
Identify the products B and C and discuss their significance.
[1+2=3]
17.
According to Global Hunger Index 2014 two billion people suffer from hidden hunger. Apply
your knowledge of plant breeding techniques to suggest a programme to improve public
health. Specify four objectives of the programme. Also mention one example of such a
produce.
[½ +2+½=3]
18.
DNA separated from one cell, when introduced into another cell is able to bestow some of
the properties of former to the latter. What is this change called in technical terms?
Describe the experimental evidences which led to the discovery of the above phenomenon.
[1+2=3]
19.
When someone buys packets of cigarettes, cannot miss the statutory warning that is present
on the packing which warns against smoking and says how it is injurious to health. Yet,
smoking is very prevalent in our society, both among young and old. Advise the
adolescents about the importance of avoiding smoking. (Mention any six points.)
[½x6= 3]
20.
Biotechnology has helped farmers to get pest resistant cotton crops. Explain the technique
adopted along with its mode of action. (Mention six points)
[½x6= 3]
OR
(a)
Draw the figure of vector pBR322 and label the following:
Origin of replication
Ampicillin resistance site
Tetracycline resistance site
Bam H1 restriction site
(b)
Identify the significance of Origin of replication
[½x4+1= 3]
21.
(a)
Given below is a single stranded DNA molecule. Frame and label its sense and
antisense RNA molecule.
5’ ATGGGGCTC 3’
(b)
sense
How the RNA molecules made from above DNA strand help in silencing of the
specific RNA molecules?
[2+1=3]
22.
Rajesh was doing gel electrophoresis to purify DNA fragments. Given below is the sketch of
the observations of the experiment performed by him.
(a)
At which end he would have loaded the samples and where?
(b)
Analyse the reason for different positions taken up by the DNA bands.
(c)
Elaborate the step he would have followed to visualize DNA bands.
[1+1+1=3]
SECTION -D
23.
Mohit and Sumit want to buy a new car for their company. Mohit insisted on buying a CNG
car with a better mileage but Sumit insisted on buying a diesel version of a high end car
with better music system and A.C but relatively low mileage.
(a)
Being a responsible citizen of Delhi, how will Mohit convince Sumit about his
decision in the wake of rising pollution levels.
(b)
What qualities of personality are being exhibited by Mohit in doing so?
(c)
Suggest two more measures which can help in reducing vehicular pollution.
[1+1+2=4]
SECTION -E
24.
Human female is not fertile after menopause whereas males can produce gametes at any
age after puberty. Analyse the statement and schematically represent a comparison
between gametogenesis in males and females.
[5]
OR
A village health worker was taking a session with women. She tells the women that one has
to be very careful while using oral pills as method of birth control. Wrong usage can actually
promote conception.
(a)
Analyze the statement and compare the merits and demerits of using oral pills and
surgical methods of birth control.
(b)
25.
Village women were confused as to how a thin metallic Copper loop can provide
protection against pregnancy. Justify the use explaining the mode of action of IUDs.
[3 +2 =5]
Observe the representation of genes involved in the lac operon given below -
i
P
p
oo
z
y
a
(a)
Identify the region where the repressor protein will attach normally.
(b)
Under certain conditions repressor is unable to attach at this site. Explain.
(c)
If repressor fails to attach to the said site what products will be formed by z, y and
a?
(d)
Analyze why this kind of regulation is called negative regulation.
[½ +1+1½+2=5]
OR
Transcription in eukaryotes is more complex process than in prokaryotes. Justify and
compare the initiation, elongation and termination in bacterial cells with eukaryotes.
[1+1+1+2=5]
26.
The graph below shows species –area relationship:
(A)
(B)
If b denotes the relationship on log scalei)
Describe a and b.
ii)
How is slope represented? Give the normal range of slope.
iii)
What kind of slope will be observed for frugivorous birds and mammals in a
tropical forest?
Species diversity of plants (22%) is much less than that of animals (72%). Analyze
the reasons for greater diversity of animals as compared to plants.
[3+2=5]
OR
(a)
(b)
Which of the above represents the increase or decrease of population?
If N is the population density at time t, then what would be its density at time (t+1)?
Give the formula.
(c)
(d)
In a barn there were 30 rats. 5 more rats enter the barn and 6 out of the total rats
were eaten by the cats. If 8 rats were born during the time period under
consideration and 7 rats left the barn, find out the resultant population at time (t+1).
If a new habitat is just being colonized, out of the four factors affecting the
population growth which factor contributes the most?
[1+1+2+1=5]
***
Sample Question Paper
Class XII (2015-16)
Biology (044)
Marking Scheme
Section - A
1. a) sex-linked
b) Haemophilia/ Colour blindness
½
½
2. It remains active during the high temperature induced denaturation of double stranded
DNA.
1
3. Incentives given to couples with small families /media publicity – posters of happy
couples with two children( slogan- Hum Do Humare Do)./ Motivate to promote smaller
families by using contraceptive methods
(Any two)
(½ x2)
4. Thymus provides micro-environment for the development and maturation of Tlymphocytes; its degeneration will weaken the immune system so the child will be
prone to frequent infections.
(½x 2)
5. Down’s Syndrome
1
Section - B
6. Pollen has an outer layer called exine which is made of sporopollenin.
½
Most resistant organic material known/ withstand high temperature, strong acids and
alkali/ no enzyme that degrades sporopollenin so far known.
(Any three)
(½x3=1½)
7. Since RNA was unstable and prone to mutations, DNA evolved from RNA with
chemical modifications that make it more stable.
DNA has double stranded nature and has complementary strands. These further resist
changes by evolving a process of repair.
(1+1=2)
8. Spirulina is a source of food rich in protein, minerals, fats, carbohydrates and vitamins,
It can grow on waste water from potato processing plants, straw, molasses, animal
manure and even sewage, so it also reduces water pollution.
(1+1)
OR
Pollination management, versatile use of resources, production at no cost (any two)
(1+1)
9.
He can grow thousands of plants through tissue culture of meristem by micropropagation/He can remove the meristem and grow it in-vitro using tissue
culture technique./Although the plant is infected with a virus, the meristem
(apical and axillary) is free of viruses.
(1+1)
10.
Besides acting as ‘conduits’ of energy transfer across trophic levels, predators
play other important roles like
 They keep prey population under control
 Predators also help in maintaining species diversity in a community by reducing
the intensity of competition among competing prey species
(1+1)
Section - C
11.
i) Pollen release and stigma receptivity is not synchronised
ii) Anther and stigma are placed at different position
iii) Self Incompatibility
iv) Production of unisexual flowers
(Any three)
(1+1+1)
12.
After implantation interdigitation of maternal & foetal tissues results in
formation of structural and functional unit between embryo & maternal body
called placenta.
1
It facilitates supply of oxygen and nutrients to the embryo, Removal of carbon
dioxide and excretory material, Also acts as an endocrine tissue and produces
hormones like HCG, hPL, estrogen. Progesterone, relaxin
(1+1)
13.
The first pyramid of biomass corresponds to a terrestrial ecosystem. Second
pyramid refers to a small standing crop of phytoplankton supporting a large
standing crop of zooplankton/aquatic ecosystem.
Top
Consumer( 2J)
Secondary
Consumer (20J)
Primary Consumer (200J)
Producer (2000J)
200,000J of sunlight
(1+2)
14.
a) Centrifugation in a CsCl density gradient.
b) After 20 mins Hybrid 14 N15 N .
15.
1
After 40 mins 50% hybrid 14 N15 N, 50% light 14 N14N
2
a)He could not get desired results because:
i) O2 was used instead of H2
ii) Temperature maintained was 800c instead of 8000.
1
b) It was concluded that life could have come from pre – existing non living
organic molecules and their formation was preceded by chemical evolution
1
c) He observed formation of Amino acids when in a closed flask CH4, H2, NH3 and
water vapour were heated at 8000 C in presence of electric discharge. Analysis of
meteorite content also reveals similar compounds indicating that similar process
are occurring elsewhere in space / Chemical evolution. Urey & Miller proved that
life originated abiogenetically whereas theory of spontaneous generation
emphasized that units of life called spores were transferred to different planets
including Earth.
1
16.
a) A is the floating cover which is placed over the slurry, which keeps on rising as
the gas is produced in the tank due to the microbial activity.
b) B is the biogas which is a mixture of gases consisting of methane, hydrogen
sulphide and carbon dioxide. It can be used as a source of energy to nearby
houses as it is inflammable.
C is the spent slurry or sludge which is removed through another outlet and may
be used as fertiliser.
(1+2 =3)
17.
Biofortification / Breeding crops with higher levels of vitamins and minerals, or
higher protein and healthier fats
½
Breeding for improved nutritional quality is improving –
(i) Protein content and quality; (ii) Oil content and quality; (iii) Vitamin content;
and (iv) Micronutrient and mineral content.
2
In 2000, maize hybrids that had twice the amount of the amino acids, lysine and
tryptophan, compared to existing maize hybrids were developed. /Wheat
variety, Atlas 66, having a high protein content, has been used as a donor for
improving cultivated wheat. / It has been possible to develop an iron-fortified
rice variety containing over five times as much iron as in commonly consumed
varieties./ The Indian Agricultural Research Institute, New Delhi has also
released several vegetable crops that are rich in vitamins and minerals, e.g.,
vitamin A enriched carrots, spinach, pumpkin; vitamin C enriched bitter gourd,
bathua, mustard, tomato; iron and calcium enriched spinach and bathua; and
protein enriched beans – broad lablab, French and garden peas.
(Any one example)
½
18.
Transformation
1
Griffith experiment
Avery, Macleod and Mc Carty identified the biochemical nature of transforming
principle i.e. DNA (brief explanation)
2
19.
 Tobacco in cigarettes contains a large number of chemical substances including
nicotine, an alkaloid.
 Nicotine stimulates adrenal gland to release adrenaline and nor-adrenaline into
blood circulation, both of which raise blood pressure and increase heart rate.
 Smoking is associated with increased incidence of cancers of lung, urinary
bladder, throat and oral cavity.
 It is responsible for bronchitis and emphysema.
 It is associated with increased risk of coronary heart disease, gastric ulcer, etc.
 Smoking increases carbon monoxide (CO) content in blood and reduces the
concentration of haem-bound oxygen. This causes oxygen deficiency in the body.
(½ X 6 =3)
20.
 The technique involves the use of a popularly known bio pesticide Bt toxin
produced by bacteria Bacillus thuriengiensis.
 Bt toxin protein when ingested by the insect gets converted to its active form due
to alkaline pH of the gut.
 The activated toxin binds to the surface of midgut epithelial cells
 It creates pores in these cells that cause swelling and lysis and eventually kills
the insect.
 The genes (cry genes) encoding this protein are isolated from the bacterium and
incorporated into crop plants like cotton.The proteins encoded by these cry
genes control the pest.
 Specifically, cry I Ac and cry II Ab control cotton bollworm (Helicoverpa
armigera), an insect belonging to Lepidoptera which earlier used to destroy the
(½x 6 = 3)
whole crop.
OR
a)
b)
Origin of replication is responsible for controlling the copy number of the
DNA sequence inserted.
1
21.
a) 5’ ATGGGGCTC 3’
sense
3’ TACCCCGAG 5’ antisense
RNA
5’AUGGGGCUC 3’
3’UACCCCGAG 5’
sense
antisense
2
b) The two strands of RNA (i.e. sense and antisense) being complementary will bind
with each other and form double stranded RNA as a result its translation and protein
expression would be inhibited.
1
22.
a) He would have loaded the samples near end A; in the wells.
b) The DNA fragments separate (resolve) according to their size through sieving
effect provided by the agarose gel. Hence, the smaller the fragment size, the
farther it moves.
c) After staining the DNA with ethidium bromide followed by exposure to UV
radiations the DNA bands appear coloured.
(1x3)
Section - D
23.
a) Mohit will give following reasons:
 CNG burns most efficiently, unlike petrol or diesel, in the automobiles and very
little of it is left unburnt.
 CNG is cheaper than petrol or diesel , cannot be siphoned off by thieves and
adulterated like petrol/ Diesel.
(Any one)
b) Mohit shows: concern towards environment, awareness towards sustainable
development.
(Any two)
c) Phasing out of old vehicles, use of unleaded petrol, use of low sulphur petrol/
diesel, use of catalytic converters in vehicles and application of stringent
pollution level norms for vehicles.
(Any two)
(1+1+2)
24.
Oogenesis is initiated during embryonic development stage when a couple of
million gamete mother cells (oogonia) are formed within each foetal ovary; No
more oogonia are formed and added after birth. A large number of these follicles
degenerate from birth to puberty. Therefore at puberty only 60,000 to 80,000
primary follicles are left in each ovary.
1
Menstrual cycle ceases after around 50 years of age and after this female is no
more fertile as cannot do ovulation whereas in males at puberty,
spermatogonia multiply by mitosis and increase in numbers, some of which
periodically undergo meiosis throughout the life.
1
(Any three similarities)
(Any three differences)
(½x3=1½)
(½x3=1½)
//
Representation through diagram
OR
a)
Contraceptive pills
Merits

demerits


Pills are effective with lesser
side effects & well accepted
by females
Reversible method
If not taken on right days
Surgical method


Surgical intervention
block gamete transport
Highly effective

Not Reversible

they can promote conception
Can have side effects if taken
for a long time

Can affect health of a
person if performed in
unhygienic condition
b)
Mode of action of IUDs
i. Increase Phagocytosis of sperms within the uterus.
ii. Cu++ released suppress sperm motility / fertility capacity of sperm
iii. Hormone releasing IUDs make uterus unsuitable for implantation /cervix
hostile to the sperm.
(3+2)
(Any two)
25.
a)
Operator region O
b)
In presence of an inducer- Lactose.
c)
Z-β galactosidase
Y- permease
a-Transacetylase
d)
It is called negative regulation as it involves constitutive (all the time)
repressor. The operon is always in off position due to presence of
repressor and is switched on only in presence of an inducer. Inducer
Lactose or allolactose interacts with repressor making it inactive.
(½ +1+1½ +2)
OR
Transcription is more complex in eukaryotes due to following reasons:
a) In prokaryotes only one type of RNA polymerase is involved whereas in
eukaryotes three types of RNA polymerases are involved.
1
b) Description of processing of hnRNA is involved-introns/ exons/ splicing is
involved in eukaryotes.
1
26.
c) Description of capping and tailing
1
d) Diagram
2
A. i) a-S=CA2
1
ii) b=log S=log C+ Z log A
1
Slope-Z( regression coefficient)
iii)Value of Z=1.15(frugivorous birds)
(normal value 0.6to 1.2)
1
B.
 Animal are mobile- can avoid predator or unfavourable event.
 Well developed Nervous system to receive stimuli against external factors
and respond to them
2
a)
b)
c)
d)
OR
a and d represents increase of population and b and c represent decrease of
population.
N t+1 = N t + [( B+I)- ( D + E) ]
Here N t=30; I=5; E=7 ;D=6 ; B=8
Putting the value in N t+1 = N t + [( B+I)- ( D + E) ]
N t+1 = 30+ [(8+5)-(6+7)]
=30+[13-13]
= 30+0=30 rats
Immigration contributes the most.
[1+1+2+1]
***